Light-sensitive silver halide materials

ABSTRACT

PHOTOGRAPHIC LIGHT-SENSITIVE MATERIALS ARE DESCRIBED WHICH INCLUDE A URETHAN WHICH IS THE REACTION PRODUCT OF (1) AN ALKOXY POLYETHYLENE GLYCOL ESTER OF ISOCYANATOACETIC ACID HAVING THE FORMULA   R-O-(CH2-CH2-O)N-(CH2)2-OOC-CH2-N=CO   WHEREIN   R REPRESNETS AN ALKYL RADICAL HAVING FROM 1 TO 5 CARBON ATOMS, AND N REPRESENTS AN INTEGER OF FROM 1 TO 35, AND   AN UNSUBSTITUTED, SATURATED, ALIPHATIC ALCOHOL; OR (2) AN ISOCYANATE AND AMONO-ALKYL ETHER OF POLYOXYETHYLENE GLYCOL. THESE MATERIALS UPON DEVELOPMENT WITH A HYDROQUINONE-FORMALDEHYDE-BISULPHITE DEVELOPER ARE SUBSTANTIALLY FREE OF &#34;PEPPERS.&#34;

United States Patent US. Cl. 9666.3 15 Claims ABSTRACT OF THE DISCLOSUREPhotographic light-sensitive materials are described which include aurethan which is the reaction product of (1) an alkoxy polyethyleneglycol ester of isocyanatoacetic acid having the formula R represents analkyl radical having from 1 to 5 carbon atoms, and n represents aninteger of from 1 to 35, and

an unsubstituted, saturated, aliphatic alcohol; or (2) an isocyanate anda mono-alkyl ether of polyoxyethylene glycol. These materials upondevelopment with a hydroquinone-formaldehyde-bisulphite developer aresubstantially free of peppers.

This invention relates to novel polyoxyalkylene derivatives,photographic materials comprising such polyoxyalkylene derivatives andto the development of exposed silver halide emulsions in the presence ofthese derivatives.

It is known that the development of continuous tone images by means of ahydroquinone p-methyl-aminophenol developer is accelerated under theinfluence of polyoxyalkylene compounds having a molecular weightpreferably above 1500. When, however, such polyoxyalkylene compounds areused in combination with a formaldehydehydroquinone-bisulfite developeras known from the German Pat. No. 1,141,531 filed Jan. 24, 1962 byPerutz Photowerke G.rn.'b.H., an increase of the gradation together witha desensitisation is obtained. The latter combination is found to bevery suitable for the development of light-sensitive materials suitedfor use in the graphic art on account of the very contrasty developmentobtained therewith. As light-sensitive materials for the reproduction ofgraphic line or screen images silver chloride and silver chlorobromideemulsions are generally employed.

The quality of a developed dot screen print is judged of by the dotsharpness. As described by J.A.C. Yule, J. Franklin Institute, vol. 239,p. 223 development of graphic materials with a hydroquinoneformaldehydebisulphite developer easily gives rise to the formation of peppers.Peppers are black spots of a very high density which are irregularlyproduced during the development in the areas of the light-sensitiveemulsion which are rather slightly exposed.

'Ihese peppers when they are present in a high amount are markedlydegrading the quality of a screen image reproduction by deforming thescreen dots and/or soiling the areas which were practically not exposed.The phenomena pepper particularly arises in the case partly aerialoxidized or rather exhausted developing baths are used. Knownpolyoxyalkylene compounds and derivatives used as developingaccelerators greatly increase the formation of peppers.

It has been found now that the development of line and/or screen imagesin silver chloride and silver chlorobromide emulsions with ahydroquinone-formaldehyde bisulphite developer, which is combined with aproduct formed by the reaction of a mono-isocyanate containingoxyalkylene groups with an alcohol or a glycol or obtained by thereaction of a mono-isocyanate or a di-isocyanate with a monoether of apolyoxyalkylene glycol, e.g. a monoalkoxy polyoxyethylene glycol, isvery contrasty, yields very sharply defined screen dots and occurs withthe formation of a smaller number of peppers as is the case with knownpolyoxyalkylene development accelerators, and furthermore can take placewithin a broad interval of time without harm to the image quality.Comparative tests described furtheron prove the technical progress ofdeveloper combinations according to the present invention as comparedwith developer combinations with known polyoxyalkylene glycols andderivatives thereof.

Products which can 'be used according to the present invention are moreparticularly:

(a) urethans formed by allowing to react an alkoxy polyethylene glycolester of isocyanato-acetic acid corresponding to the following formula:

R represents an alkyl radical preferably having 1 to 5 carbon atoms, and

n represents a positive integer from 1 to 35, preferably from 8 to 20,

with alcohols such as methanol, ethanol, propanol, hexadecylol, or withpolyols such as ethylene glycol, glycerol etc.

(b) bisurethans formed by reaction of diisocyanates such as2,5-diisocyanato-toluene or 1,6-diisocyanato-n-hexane withpolyoxyethylene glycol ethers having a molecular weight preferablycomprised between and 1000, in which one of the terminal hydroxyl groupsis rendered non-reactive in respect of isocyanato groups e.g. byetherification with an alcohol having preferably 1 to 5 carbon atoms.

By way of illustration the preparation of some monoand diurethanpolyoxyalkylene compounds according to the present invention will now bedescribed. As will be appreciated, mixtures of the monoand di-urethanpolyoxyalkylene compounds may be formed depending upon the proportionsof the reactants.

PREPARATION 1 Urethan formed from ethanol and a methoxy polyethyleneglycol isocyanato-acetate.

(a) Methoxy polyethylene glycol bromo-acetate 147 g. (0.2 mole) ofmethoxy polyethylene glycol (average molecular weight 750) are dissolvedin 500 ccs. of benzene and 31.5 g. (0.2 mole) of bromoacetyl chlorideare added to this solution whilst stirring. A nitrogen flux is conductedthrough the reaction mixture for eliminating the evolving hydrochloride.The reaction mixture is heated to 60 C. and boiled for 2 hours in orderto eliminate all of the hydrogen chloride. Subsequently the benzene isdistilled off and the residue is utilised for the preparation of:

(b) Methoxy polyethylene glycol isocyanato-acetate 1779 g. of methoxypolyethylene glycol bromo-acetate are dissolved in 4.5 litres ofanhydrous ether and 162 g. of finely divided potassium isocyanate areadded whilst stirring. The reaction mixture is refluxed for 40 hours. Anamount of 162 g. of potassium isocyanate is added yet and refluxing iscontinued for 24 hours. After having been cooled, the ether layer isseparated as completely as pos- 3 sible. The remaining reaction mixtureis diluted with 5 litres of benzene. The precipitated potassium bromideis filtered off and the benzene filtrate is evaporated in vacuo. Theresidue is dried in vacuo.

CH3O(CHzCH2O)mO O CHzNI-IO OOC2H5 PREPARATION 2 Urethan formed fromn-hexadecylol and methoxy polyethylene glycol isocyanato-acetate.

CH O-(CH CH O) COCH NHCOOC H -n 25 g. (0.03 mole) of methoxypolyethylene glycol isocyanato-acetate prepared as described inPreparation 1 (b) are dissolved in 100 ccs. of anhydrous benzene. Then7.3

4 PREPARATION 5 Diurethan formed from polyethylene glycol with anaverage molecular weight of 1000 and methoxy polyethylene glycolisocyanato-acetate (3H2 (IJH $0 ('30 (OCI-IzCHz)raOCHa (O CHzOHzlmOCHa25 g. (0.03 mole) of methoxy polyethylene glycol isocyanato acetate aredissolved in 100 ccs. anhydrous ben zene. Then g. of polyethylene glycolwith an average molecular weight of 1000 are added and the mixture isrefluxed for 2 hours on a water bath. The benzene is distilled off invacuo. Yield: 48.5 g.

PREPARATION 6 Diurethan formed from methoxy polyethylene glycol and2,S-diisocyanato-toluene.

150 g. (0.2 mole) of methoxy polyethylene glycol with an averagemolecular Weight of 750 are dissolved in 150 ccs. of anhydrous benzene.Then 17.4 g. (0.1 mole) of 2,5-diisocyanato-toluene dissolved in 50 ccs.of benzene are added. The temperature of the reaction mixture ismaintained between 27 and 30 C. by cooling with ice- Water till theexothermic reaction is terminated. The reaction mixture is refluxed foranother 105 minutes. The benzene is distilled off in vacuo on a Waterbath at 50 C.

Yield: 155 g.

The total reaction is as follows:

no 0 omo onomo-nwmornon -om the O lTIHCOOCHzCHg (OCHzCHz) 5-OCHa g. ofn-hexadecylol are added and the reaction mixture is refluxed for 2 hourson a water bath. Subsequently the benzene is distilled off in vacuo.Yield: 30.5 g.

PREPARATION 3 Diurethan formed from ethylene glycol and methoxypolyethylene glycol isocyanato-acetate.

OHQO (CH2CH20)10COCHzNHCOOfiIHz CHaO(CH2CH2O)mCOGHzNHOOO-CHz 25 g. (0.03mole) of methoxy polyethylene glycol isocyanato-acetate prepared asdescribed in Preparation 1 (b) are dissolved in 100 ccs. of anhydrousbenzene. Then 18 g. of ethylene glycol are added and the reactionmixture is refluxed for 2 hours on a Water bath. The benzene isdistilled off in vacuo. Yield: 23.5 g.

PREPARATION 4 Diurethan formed from polyethylene glycol with an averagemolecular weight of 300 and methoxy polyethylene glycolisocyanato-acetate 25 g. (0.03 mole) of methoxy polyethylene glycolisocyanato-acetate are dissolved in 100 ccs. of anhydrous benzene. Then9 g. of polyethylene glycol with an average molecular weight of 300 areadded and the resulting mixture is refluxed for 2 hours on a water bath.The benzene is distilled oif in vacuo. Yield: 31 g.

PREPARATION 7 Diurethan of methoxy polyethylene glycol and 1,6-diisocyanato-hexane.

150 g. (0.2 mole) of methoxy polyethylene glycol with an averagemolecular weight of 750 are dissolved in 150 ccs. of anhydrous benzene.Then a solution is added of 16.8 g. (0.1 mole) of1,6-diisocyanato-hexane in 50 ccs. of anhydrous benzene. The reactionmixture is refluxed for min. The benzene is distilled 0E in vacuo on awater bath at 50 C. Yield: 166 g.

The urethans used according to the present invention can be added to thesilver halide emulsions or can be incorporated into a water-permeablelayer under or on top of the emulsion layer, which Water-permeable layerstand in water-permeable relationship with the emulsion layer.

Preferably the said products are added to the lightsensitive silverhalide emulsions in dissolved form in water or a mixture of water andwater-miscible organic solvents, which do not impair the photographiccharacteristics of the emulsion.

However, these products can also be incorporated into the emulsion byimbibition by treating it with a solution containing these products orby diffusion from an adjacent Water-permeable layer comprising theseproducts.

The water-soluble urethans used according to the present invention canbe added to the light-sensitive silver halide emulsion during differentpreparation steps of the light-sensitive material. For example they canbe incorporated therein by a separate addition or they can be added as amixture with one or more ingredients used in the formation of the silverhalide grains, during the physical or chemical ripening or duringanother step preceding the coating of the emulsion.

The said products are preferably added to the emulsion after thechemical ripening and just before the coating of the emulsion.

The optimun amount of the urethans to be added to the emulsion dependson the very compound, on the nature of the colloid binder of the silverhalide grains and on the amount and type of silver halide in theemulsion. In general, however, the above urethan products are added tothe light-sensitive material in an amount of 1 mg. to 10 g. per mole ofsilver halide. When incorporated into the developer they are used inamounts ranging from 50 mg. to 20 g. per litre of developer. Ifnecessary, amounts exceeding these limits can be used as well.

The increase of the dot defininition and development latitude obtainedwith urethan products according to the present invention can be combinedwith a chemical sensitisation by using in combination with theabovementioned urethan products chemical sensitising agents such assulphur-containing compounds e.g. allyl isothio cyanate, allyl thioureaor sodium thiosulphate, reducing agents such as the tin compoundsdescribed in the Belgian patent specifications 493,464, filed Jan. 24,1950 and 568,687, filed June 18, 1958 by Gevaert Photo-Producten N.V.,the imino-amino methane sulphinic acid compounds described in theBritish patent specification 789,823, filed Apr. 29, 1955 by GevaertPhoto-Producten N.V. or precious metal compounds such as gold, platinum,palladium, iridium, ruthenium and rhodium compounds. The sensitisingaction also manifests itself, of course, when combing theabove-mentioned urethan products with the sensitising compounds presentby nature in gelatin.

The urethan products according to the present invention can also be usedin combination with stabilising agents for silver halide emulsions, suchas mercury compounds and the compounds described in the Belgian patentspecifications 571,916 and 571,917, filed Oct. 10, 1958 by GevaertPhoto-Producten N.V., and in combination with sensitising andstabilising cadmium salts in the lightsensitive material as well as inthe developer.

Water-soluble compounds, which also accelerate the development, such asthose described e.g. in the British patent specification 954,205, filedJune 30, 1960 by Gevaert Photo-Producten N.V. can be applied togetherwith the urethans according to the present invention in a developingbath as well as in the light-sensitive material.

Together with the above-mentioned urethan products, derivatives oftetra-azaindenes having the following general formula can be used asfog-inhibiting compounds:

wherein each of R and R represents a hydrogen atom, an alkyl,

an aralkyl, or an aryl radical, and

R represents a hydrogen atom, an alkyl, a carboxy or an alkoxy carbonylgroup.

Such compounds can be prepared shtarting from 1 mole of fl-ketoester ora a-ethoxymethylene-B-ketoester with 1 mole of a suitable3-amino-1,2,4-triazole. By way of example of such derivatives5-methyl-7-hydroxy-s-triazolo- (l,5-a)-pyrimidine can be mentioned.

Other agents such as hardening agents, wetting agents, plasticisers,developing agents, and optical sensitising agents can be incorporatedinto the emulsion in the usual way.

The urethans according to the present invention can preferably be usedin the development of screen prints on silver chloride and silverbromo-chloride emulsions with a hydroquinone-formaldehyde-bisulphitedeveloper, but they can also be used in combination with silver halideemulsions of any other type.

The following examples illustrate the invention.

EXAMPLE 1 After ripening of a green-sensitised silver chlorobromideemulsion (35 mole percent of bromide) containing5-methyl-7-hydroxy-s-triazolo-( l,5-a)-pyrimidine and cadmium chloride,a polyoxyalkylene derivative listed in the following Table 1 is added.After the addition of the usual wetting agent, of 25% by weight of alatex-plasticiser calculated on the weight of gelatin, and of ahardening agent such as formaldehyde and glyoxal, the emulsion samplesare coated in the same way on a cellulose triacetate support and dried.

The latex-plasticiser consists in a latex of a 20% by weight aqueousdispersion of poly(ethyl acrylate) prepared according to knowntechniques of emulsion polymerisation carrying out the polymerisation inthe presence of 8% by weight calculated on the monomer of an emulsifyingagent of one of the following types: the condensation product of oleicacid and methyltaurine, the sodium salt of l-aurylsulphonic acid or thesodium salt of an alkylbenzene sulphonic acid wherein the alkyl radicalcontains from 8 to 12 carbon atoms.

The light-sensitive material is exposed through a continuous wedge and aglass screen by means of a lightsource having a colour temperature of37CO K. The exposure is regulated such that the wedge print of thescreen embraces the beginning of dot formation as well as thedisappearance of the high lights.

The development is performed at 20 C. in a developing bath having thefollowing composition:

Water to 1000 ccs.

The appreciation of the dot definition occurs visually by comparisonwith standard materials, which in decreasing order of dot definitionquality are indicated with the numbers 1, 2, 3 and 4.

The appreciation of the peppers occurs visually after exposure of thelight-sensitive materials through a step wedge and without screen anddevelopment for 2.5 min. at 20 C. in the above-mentioned developer,which previously has been deactivated, by developing therein 0.32 sq. m.of completely exposed graphic film per liter.

The numbers 0 to 4 represent the number of peppers:

0=no peppers 1=very few 2=few 3=many (material no longer suitable forreproduction) 4=very much (useless material).

TABLE 1 D 01: definition after a development time of-- Mg. ofoxyalkylenc condensation product per mole of silver halide Pep- 3 min.pers 2 min.

7 EXAMPLE 2 Example 1 is repeated with a similar type of emulsion butthe polyoxyalkylene derivatives stated in Table 2 are used.

TABLE 2 Dot sharpness after a development time of- Mg. of oxyalkylenecondensation product Pepper mole of silver halide 3 min. 3.5 min. pers100 mg. of the condensation product of 1 mole of maleic anhydride and 1mole of polyethylene glycol having an average molecular Weight of 2,000prepared in an analogous way to preparation 3 of the British patentspecification 920,637 filed May 7, 1959 by Gevaert Photo'Producten N.V 11 2. 5 140 mg. of the condensation product according to preparation 3 11 0. 9

EXAMPLE 3 Example 1 is repeated with the same emulsion type, but thepolyoxyalkylene derivatives listed in Table 3 are used.

TABLE 3 Dot definition after a developing time oi Mg. of oxyalkylenecondensation Pepproduct per mole of silver halide 2.5 min. 3 min. 3.5min. pers 30 mg. oi the condensation product according to preparation 31 2 1. 40 mg. of the condensation product according to preparation 1 2 10 R represents an alkyl radical having from 1 to carbon atoms, and nrepresents an integer of from 1 to 35 and an unsubstituted, saturated,aliphatic mono, di or trihydric alcohol or polyethylene glycol; or (2) amonoor di-isocyanate and a mono-alkyl ether of a polyoxyethylene glycolhaving a molecular weight of from about 100 to 1,000, said alkyl beingfrom 15 carbon atoms.

2. The light-sensitive material of claim 1 wherein the alcohol is analcohol having only one hydroxy group.

3. The light-sensitive material of claim 1 wherein the alcohol is apolyol.

4. The light-sensitive material of claim 1 wherein the isocyanate is amono-isocyanate.

5. The light-sensitive material of claim 1 wherein the isocyanate is adi-isocyanate.

6. The light-sensitive material of claim 1 wherein said emulsion layerincludes silver chloride or silver chlorobromide and said urethan isreaction product (1).

7. The light-sensitive material of claim 1 wherein said emulsion layerincludes silver chloride or silver chlorobromide and said urethan is thereaction product (2).

8. The light-sensitive material of claim 1 wherein said urethan ispresent in an amount of from 100 milligrams to 100 grams per mole ofsilver halide.

9. A photographic hydroquinone-formaldehyde-bi-sulphi-te developercontaining a monoor (ii-urethan which is 8. the non-polymeric reactionproduct of (1) an alkoxy polyethylene glycol ester of isocyanato-aceticacid having the formula wherein:

R represents an alkyl radical having fro 1 to 5 carbon atoms, and

n represents an integer of from 1 to 35 and an unsubstituted, saturated,aliphatic mono, di or trihydric alcohol or polyethylene glycol; or (2) amonoor di-isocyanate and a mono-alkyl ether of polyoxyethylene glycolhaving a molecular weight of from about to 1,000, said alkyl being from1-5 carbon atoms.

10. The developer of claim 9 wherein urethan is present in an amount offrom 50 milligrams to 20 grams per litre.

11. A process for developing photographic materials containing alight-sensitive silver halide in which a photographic silver chloride orsilver chlorobromide emulsion sutable for the production of line andscreen prints is developed with a hydroquinone-formaldehyde-bisulphitedeveloper characterized in that the development is carried out in thepresence of a monoor di-urethan which is the non-polymeric reactionproduct of (1) an alkoxy polyethylene glycol ester of isocyanate-aceticacid having the formula R represents an alkyl radical having from 1 to 5carbon atoms, and n represents an integer of from 1 to 35 and anunsubstituted, saturated, aliphatic mono, di, or trihydric alcohol orpolyethylene glycol; or (2) a monoor di-isocyanate and a mono-alkylether of a polyoxyethylene glycol having a molecular weight of fromabout 100 to 1,000, said alkyl being from 1-5 carbon atoms. 12. Theprocess of claim 11 wherein the alcohol is an alcohol having only onehydroxy group.

13. The process of claim 11 wherein the alcohol is a polyol.

14. The process of claim 11 wherein the development is carried out inthe presence of reaction product (1).

15. The process of claim 11 wherein said urethan is reaction product(2).

References Cited UNITED STATES PATENTS 3,030,209 4/1962 Henn 9666.33,038,804 6/ 1962 Knox 96- 107 3,150,977 9/1964 Hart 96107 3,158,48411/1964 Williams 96-114 3,158,484 11/1964 Willems 96--114 3,307,9483/1967 Thiers 96--66.3 2,531,832 11/1950 Stanton 9666.3

FOREIGN PATENTS 1,122,834 11/1962 Germany. 1,305,017 8/1962 France.

NORMAN G. TORCHIN, Primary Examiner M. F. KELLEY, Assistant ExaminerU.S. Cl. X.R. 9695, 107

